In this study patients with a brain tumor called glioblastoma multiforme that has recurred will be divided into two groups. Half of the patients will receive an investigational medicine called SU101. The other half will receive another anti-cancer drug called procarbazine (PCB), also known as Matulane. The FDA has not approved SU101. The FDA has approved PCB for use in patients with Hodgkin's disease. Other published research studies have shown that PCB may be effective in treating some brain tumors in some patients. It will also attempt to answer the following: 1) Is there a difference in the length of time it takes the tumor to begin growing again and in overall survival between: a)patients who are treated with SU101 given intravenously and b)patients who are given PCB orally? 2) What are the side effects of SU101 when given into a vein four days in a row followed by one dose every week for six weeks. 3) Is there a difference in quality of life between patients treated with SU101 and PCB?